On Mon, Sep 28, 2009 at 10:12 AM, Jacques Caron <j...@oxado.com> wrote: > Hi, > > You can use a trigger before insert and a pl/pgsql function that goes: > > BEGIN > UPDATE table SET ... WHERE pk=NEW.pk > IF FOUND THEN > RETURN NULL; > ELSE > RETURN NEW; > END IF; > END; > > Jacques.
That seems about right. It's possible that the UPDATE could fail to find any rows but the INSERT could still fail due to a duplicate key violation (consider, for example, doing inserts for the same not-previously-exstant PK value in two different transactions, and then trying to commit each one). But I don't believe there's any way to completely prevent that sort of problem in a concurrent environment short of serializing all work behind a table lock, so the best we can do is try to make errors rare and avoid silent failures, which this should do. ...Robert -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
